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PostPosted: Sun Jul 26, 2009 6:03 pm 
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amethystguy wrote:
Don't forget to test the bananas in your kitchen after you test your topaz


Speaking of potassium... underground here in the lab I get a background reading that ranges from 40-80 counts per minute (cpm) depending on solar flares, cosmic rays etc. I tested some prehistoric sharks teeth that gave me a reading of over 150 cpm. Nothing outlandish, but at least measurable.

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PostPosted: Sun Jul 26, 2009 6:08 pm 
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Thats cool..I know that bananas coming up from central america frequently set off the radiation detectors at the border crossings...is there copius amounts of potassium in sharks teeth? I might have read somewhere that they used potassium-argon dating on shark teeth..mayeb..maybe not?

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PostPosted: Sun Jul 26, 2009 6:15 pm 
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Now you have me thinking.. it may not be K after all. Perhaps some of the radioactive folks here might shed further light?

Maybe sitting on the ocean floor for eons would make it store some U or thorium?

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PostPosted: Sun Jul 26, 2009 6:21 pm 
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I know that U will attract to and replace organic material but shark teeth I don't know

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PostPosted: Sun Jul 26, 2009 6:42 pm 
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Bear,
Since this thread is generally about topaz, here's a topaz question. Barring detectable radioactivity, is there any test to distinguish irradiated blue topaz (any kind, Sky, Swiss, London) from natural blues?

I've always assumed there were none but I keep seeing suggestions here and there that tests exist. Since so much clean white topaz is available for treating, I'd think the presence of inclusions would suggest natural blue but that's indirect evidence.

So many treatments (heat, irradiation, diffusion, azotic coating) exist for nearly every topaz color these days, including the Imperial hues, has the traditional value of this gem species been damaged in your opinion?

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PostPosted: Sun Jul 26, 2009 6:47 pm 
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http://gemologyonline.com/Forum/phpBB2/ ... rial+topaz

Robert you might want to look at this link to some of Mr. Lembeck's stones posted in a previous discussion about imperial topaz.

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PostPosted: Sun Jul 26, 2009 7:24 pm 
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Great link. Thanks so much. I did do a search before the post but some how I missed this one. Thanks! :D


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PostPosted: Sun Jul 26, 2009 9:05 pm 
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Hi Rick,

That's a good question. I don't know how much research has been done to detect the difference between naturally irradiated blues or those done by man. I would have to say that there probably is a way to tell the difference, either through gamma spectroscopy or possibly FTIR. But why bother? I would venture to say that well over 99.9% of any blue topaz is going to be irradiated. And if you do have a natural blue, it still would have to be disclosed as irradiated, albeit by nature.

The presence of inclusions (or lack of) is not an indicator of whether it is a natural or irradiated. Most all topaz is usu. very clean. They have to use naturals anyway, and the initial radiation treatment turns them a brownish color. They then anneal (heat treat) to turn them the blue color.

With regards the market and price, I would say that I don't feel the various treatments, coatings etc, has affected the value or price on the nicer imperial or precious topaz. And the blues have always been inexpensive.

You are right that there are various locale that produce lots of white topaz, but many of these are not susceptible for treatment by irradiation and are often used for the coating treatment. I would much prefer a nice well cut white topaz. How about you?

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PostPosted: Sun Jul 26, 2009 10:00 pm 
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Bear Williams- SGL wrote:
But why bother? I would venture to say that well over 99.9% of any blue topaz is going to be irradiated. And if you do have a natural blue, it still would have to be disclosed as irradiated, albeit by nature.

Natural blue topazes sell at a premium, especially if they're from Texas, as I'm sure you know. And as a couple of GO members report, premium-priced natural blues are now being found in Australia. I've also been asked by a couple of very reliable cutters to sell stones they claim are natural blues. Skeptics will still ask for proof and that was the reason for my question. Your answer is what I expected but I wanted to be sure I hadn't missed any developments along that line.

I'm not aware of any FTC regulation that requires naturally-irradiated gems to be disclosed as such.
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The presence of inclusions (or lack of) is not an indicator of whether it is a natural or irradiated. Most all topaz is usu. very clean. They have to use naturals anyway

You didn't take my point. With the abundance of very clean treatable white topaz, there would be no reason to irradiate included stone. So the presence of inclusions might be a very indirect clue that a stone is natural. But it certainly would not be proof.
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You are right that there are various locale that produce lots of white topaz, but many of these are not susceptible for treatment by irradiation and are often used for the coating treatment. I would much prefer a nice well cut white topaz. How about you?

bear

I much prefer all of my topaz to be untreated -- including Imperial. Unfortunately some Ouro Preto material is often heated to pink-red. And Richard Pollack's diffused red/pinks would seem to me to make ID-ing genuine Imperials in that hue range very tricky if sold by the unscrupulous.

Pollack's teals and glacier blues are obvious (if tested) but the Champagne yellows might also be a challenge.

To me it seems the topaz "jungle" has some very tricky new pathways.

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PostPosted: Sun Jul 26, 2009 10:15 pm 
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Rick,

Okay, yes I see your point that enough inclusions could be indirect clue to it being a natural, esp. since subsequent heating might cause internal voids to fracture. I do need to look into these natural blues more, and perhaps get some to do research on. As for the tricky stuff, I agree it is sometimes difficult to detect.

Just want to make sure terminology doesn't get in the way....when you say diffused, you are referring to the coating technology correct? We've been around the block a couple of times with the concept of diffusing of the transitional metal ions into the crystal lattice of topaz and tourmaline and we don't want to make the mistake in thinking that this is being done. :roll:

bw


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PostPosted: Sun Jul 26, 2009 11:06 pm 
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amethystguy wrote:
Don't forget to test the bananas in your kitchen after you test your topaz


:lol: after ms. barbra mentioned that regarding bananas in another post, maybe we should!


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PostPosted: Sun Jul 26, 2009 11:34 pm 
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If Cobalt-60 irradiated, a Geiger counter would not pick anything up anyways if my memory holds true.


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PostPosted: Sun Jul 26, 2009 11:59 pm 
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Bear Williams- SGL wrote:
Just want to make sure terminology doesn't get in the way....when you say diffused, you are referring to the coating technology correct? We've been around the block a couple of times with the concept of diffusing of the transitional metal ions into the crystal lattice of topaz and tourmaline and we don't want to make the mistake in thinking that this is being done. :roll:

bw


Bear, I think you should look into the patented Pollak Heat Diffusion Process, developed by Richard Pollak, San Diego. His diffused topazes were originally sold by Leslie & Co., and the company was recently sold to Signity. Diffused topazes are now being sold by Stuller, for Heaven's sake!

From the descriptions I can find the process is similar to the original sapphire diffusion method developed in the 1970s or 80s which colored only a tiny surface region of the stones. It could be removed by chipping or recutting. It's not exactly a secret; there have been stories about it in all the major trade mags.

Link to Pollack Heat Diffusion Patent

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PostPosted: Mon Jul 27, 2009 1:34 am 
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I have a couple of root beer colored topazes that have been irradiated but never heated. I left one in the sun out of curiosity and it has faded to clear. Not any sort of chemist or physicist myself but it does seem curious that heating to blue also makes the color permanent. Probably a very logical explanation from those who understand such things.

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PostPosted: Mon Jul 27, 2009 4:36 am 
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Irradiation w/ gamma rays will not leave any residual activity. However the NRC got involved at one point and I recall a 1 year "cooling" period prior to sale if it was neutron irradiated. Also some people getting burned by rocks that were not left to decay to safe levels.

If topaz was irradiated with neutron's, there would be some detectable radiation for a short while afterwards... seems that a standard pancake detector cannot resolve it though.

Ok, here's an article: here
Tantalum-182 appears to be a gamma emitter 119 day half life 1.12 Mev energy, and Manganese-56 is a beta emitter w/ a 3 hour half life.

edit: Even better information: http://adsabs.harvard.edu/abs/1991PhDT........19N

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